1. Field of Invention
The invention relates to a fan, a motor and a bearing structure thereof. In particular, the invention relates to a fan, a motor and its bearing structure that provides a pre-stress to the bearing.
2. Related Art
In the modem information era, electronic equipment has become an indispensable part of daily life and work. Motors in particular are widely used in various electronic devices to effectively convert electrical energy into mechanical energy.
There are many types of motors. FIG. 1 shows a conventional brushless motor 1. The brushless motor 1 includes a housing 10, a rotor structure 11 and a stator structure 12. The rotor structure 11 has a shaft 111 passing through the housing 10. The stator structure 12 has a coil set 121, which fits around with the housing 10. An annular magnet 112 of the rotor structure 11 is disposed corresponding to the coil set 121. The interaction between the coil set 121 and the magnet 112 generate an alternated magnetic field to rotate the rotor structure 11.
To make the motor 1 operate smoothly, a bearing 13 is generally used to cover the shaft 111. Consequently, the shaft 111 rotates well with the support of the bearing 13. As well, the bearings 13 can be classified into ball bearings, sleeve bearings and sliding bearings according to the structures thereof. Take the ball bearing as an example that has an inner ring 131, an outer ring 132 and a ball 133. The inner ring 131 is mounted on the shaft 111. The outer ring 132 is connected to the housing 10. The ball 133 is disposed between the inner ring 131 and the outer ring 132. In order to make the shaft 111 run more smoothly with the support of the bearing 13, the motor 1 further includes an elastic element 14 disposed between the bearing 13 and a cover 15. As shown in FIG. 1, the elastic element 14 presses against the inner ring 131 of the bearing 13 to provide a pre-stress to the bearing 13 so as to make the ball 133 of the bearing 13 maintains linear contact with the inner ring 131 and the outer ring 132 simultaneously. This mechanism buffers the axial load variation to the bearing 13 under the high-speed rotation of the shaft 111, thereby elongating the lifetime of the motor 1. According to the different configurations, the elastic element 14 can press against the outer ring 132 of the bearing 13 as well that provides pre-stress on the bearing 13 as shown in FIG. 2.
However, a spring is used as the elastic element 14 generally. After a long-time use of the motor 1, the continuous pressure imposed on the bearing 13 is easy to cause elastic fatigue for the elastic element 14. This seriously shortens the lifetime of use of the motor 1.
Therefore, it is an important subject to provide a fan, a motor and a bearing structure thereof that can provide a pre-stress to the bearing and prevent the elastic element from being overly pre-stressed and damaged.